Kankoku Jin (韓国人)
Korean is called Kankokujin by most Japanese people in Japanese.
In Japanese, people from that country are called by adding the country name + Jin (人).
Watashiwa Kyou、Kankokujinto Kaimononi Ikimasu。
“I will go shopping with a Korean today.”
Watashino Kareshiwa Kankokujin Desu。
“My boyfriend is Korean.”
How to say “South Korean” in Japanese
South Korean is also called Kankokujin(韓国人) in Japanese, not Minami Kankokujin(南韓国人).
How to say “North Korean” in Japanese
Romaji: Kitachousen jin,
North Koreans are called Kitachousenjin(北朝鮮人) in Japanese. Therefore, you may think that we call South Korean Minami Chousenjin(南朝鮮人), but we call it Kankokujin(韓国人) instead of calling it that way.